means for effecting rotation of a worm wheel



March 31, 1964 LEACH MEANS FOR EFFECTING ROTATION OF A WORM WHEEL 0R WORM WHEEL SEGMENT Filed Oct. 17, 1960 United States Patent 3,126,753 MEANS FGR EFFECTING RQTATION OF A WGRM WHEEL 0R WORM WHEEL SEGMENT Edward Blackweil Leach, Compton, England, assignor to Audley Engineering Company Limited, Newport, England Filed Get. 17, 1960, Ser. No. 62327 Claims priority, application Great Britain Oct. 27, 1959 2 Claims. (Cl. 74-393) This invention relates to means for effecting rotation of a worm Wheel or worm wheel segment and its is envisaged that the invention will have especial application to the operation of rotary plug valves although it is to be understood that the invention may also be applied to other apparatus and mechanisms where it is required to effect rotation.

Means according to the present invention embody a worm which is adapted to engage with the worm wheel or worm wheel segment and which is mounted on a shaft, said shaft being mounted for rotary and axial movement and there being provided a fluid pressure responsive device adapted to move said shaft and worm in an axial direction together with a fluid pressure producing device for rotating the shaft and worm, said devices being arranged so that in use the shaft and worm will be moved at any given time either in an axial direction or in an angular direction.

The arrangement may be such that the axial position of the shaft determines which of said two devices shall be effective to move the shaft and worm at any given time or alternatively, the fluid pressure may determine which of said devices shall be effective. In the former case there may be provided a pilot valve which is either mechanically connected to the shaft or alternatively which is arranged to be actuated by fluid pressure through the intermediary of a further valve which is itself actuable by axial movement of the shaft.

The invention will now be more particularly described with reference to the accompanying drawing which is a part-sectional view showing one form of means constructed in accordance with the present invention and as applied to the operation of a valve of the rotary plug type.

Referring now to the drawing, there is provided a rotary plug valve generally indicated by reference numeral having a worm wheel 11 which engages with a worm 12 mounted on a shaft 13. One end of said shaft is provided with an extension 14 to which is secured a piston 15 operating in a cylinder 16 and which defines the pressure responsive device. The opposite end of said shaft is provided with an extension 58 which is in splined connection with a sleeve 59 which is in itself in splined connection with the output shaft 60 of an hydraulic pump coupling generally indicated by reference numeral 61.

The hydraulic pump coupling 61 and which defines the pressure producing device includes an input shaft 62 on which is mounted a gear 63 engaging two gears 64 which are mounted in a housing 65 which is free to rotate about the axis of the coupling and which is connected to the aforementioned output shaft 60. By means of passages formed in the shafts 62 and 60 and in the body 66 of the pump, hydraulic fluid can be circulated so that with maximum output pressure and zero delivery a mechanical torque is delivered to said output shaft 60 or alternatively when the output pressure and mechanical torque are zero the volume of delivery will be at a maximum or as a still further alternative the pump may be operating between these two extremes so that it will supply some pressurised fluid together with some mechanical torque to the output shaft 60.

There is also provided a valve unit 67 having a springcentered spool 68 so that when the pump is put into operation one or other of the lines 69 and 76 will be con- 3,126,753 Patented Mar. 31, 1964 "Ice nected through the valve unit 67 to a reservoir via the supply connection 71.

The lines 69 and 70 are connected respectively to lines 72 and 73 which are connected to pressure relief switches 74 and 75 and to valve blocks generally indicated by reference numerals 76 and 77 mounted one on either side of the cylinder 16. Each of said valve blocks 76 and 77 contains a spring-loaded control valve 78 and a return valve 79 which are also spring-loaded so as to be biased towards the piston 15.

Assuming that the hydraulic pump unit is operating in a direction so as to supply pressurised fluid to the line 72 the valve 78 in the valve block 77 Will have pressure applied to its right hand end so that eventually it will move to the left thereby permitting fluid to enter the cylinder 16 via the left hand passages 80 and 81. This will have the effect of moving the piston 15 and with it the shaft 13 and worm 12 to the left whilst fluid is exhausted from the left hand side of the piston 15 through the valve block 76. At the same time the valve 79 in the valve block 77 moves to the left under the pressure of its spring following the piston 15 until the passage 82 communicates by a recess 83 with the passage 84 and thereby applies pressure to the left hand end of spool 78. Said left hand end has a bigger area than the right hand end so that the spool will be moved to the right thereby cutting off the supply of pressurised fluid to the right hand side of the piston 15.

Pressure now rises in the line 72 and providing the worm wheel 11 has a sufficiently high resistance to rotation the hydraulic pump unit will commence to rotate the output shaft 60 and thereby rotate the shaft 13 through the sleeve coupling 59 so that the worm will be screwed back relative to the worm wheel prior to another axial stroke of the piston 15.

In the above description it has been assumed that the strength of the spring 85 which acts on the Valve 78 relative to the resistance to rotation of the worm wheel 11 is such that said valve 78 will be moved to its operative position to permit axial movement of the shaft 13 before rotation of the shaft 60 occurs.

On the other hand if the resistance to rotation of the worm wheel 11 and associated rotary valve is relatively low or if the spring 85 is arranged to apply a relatively strong loading to the spool 78 then delivery pressure from the hydraulic pump will build up until the worm 12 I0- tates and thereby rotates the worm wheel 11 and rotary valve plug. This will continue until the rotary valve plug reaches the limit of its movement when a suitable cut-out switch can be arranged to operate or alternatively if an undue resistance to rotation of the worm wheel 11 should develop the fluid pressure will build up until the valve 78 is operated and the shaft 13 is moved axially as previously described. Thus the arrangement may be such that the worm wheel 11 is normally rotated by rotation of the worm 12, axial movement of the shaft 13 only occurring in the event of said worm wheel developing an unduly high resistance to rotation or alternatively said worm wheel 11 may be rotated by axial movement of the shaft 13 (the worm 12 then acting in the manner of a rack) rotary motion of the worm 12 being used to screw it back relative to the worm wheel for the next axial movement of the shaft.

It is, of course, to be understood that rotation of the worm wheel 11 in the opposite direction is effected by reversing the rotation of the hydaulic pump coupling and using the left hand valve block 76 in a manner similar to that described with reference to the valve block 77.

Furthermore, it is to be understood that pneumatic pressure can be used in any of the arrangements described above although it is preferred that hydraulic fluid shall be used.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

1. Mechanism for effecting rotary motion of a toothed worm gear member, comprising in combination with said toothed worm gear member, an axially movable and rotatable worm in continuous engagement with said toothed worm gear member so that said worm can serve to impart rotary motion to said toothed worm gear member when said worm is moved axially Without being rotated, and also when said worm is rotated without being moved axially, a rotatable and axially movable shaft on which said worm is secured, a fluid pressure producing means operably connected to said shaft for imparting rotary motion thereto, a fluid pressure responsive means also operably connected to said shaft for imparting axial motion thereto, valve means responsive to the pressure produced by the fluid pressure producing means for controlling fluid flow to and from the fluid pressure producing means and 4% the fluid pressure responsive means, and additional means responsive at the terminal positions of the worm whereby the Worm is returned to its initial position for subsequent axial movement.

2. Mechanism according to claim 1, and comprising in combination a fluid pump coupling which defines said fluid pressure producing means, and valves constituting said valve means which are responsive to the delivery pressure of said fluid pump coupling, and under the control of which fluid is admissible to said fluid pump coupling, and pressurized operating fluid is admissable to said pressure responsive means from said fluid pump coupling.

References Cited in the file of this patent UNITED STATES PATENTS 

1. MECHANISM FOR EFFECTING ROTARY MOTION OF A TOOTHED WORM GEAR MEMBER, COMPRISING IN COMBINATION WITH SAID TOOTHED WORM GEAR MEMBER, AN AXIALLY MOVABLE AND ROTATABLE WORM IN CONTINUOUS ENGAGEMENT WITH SAID TOOTHED WORM GEAR MEMBER SO THAT SAID WORM CAN SERVE TO IMPART ROTARY MOTION TO SAID TOOTHED WORM GEAR MEMBER WHEN SAID WORM IS MOVED AXIALLY WITHOUT BEING MOVED AXIALLY, A ROTATABLE AND AXIALLY MOVABLE SHAFT ON WHICH SAID WORM IS SECURED, A FLUID PRESSURE PRODUCING MEANS OPERABLY CONNECTED TO SAID SHAFT FOR IMPARTING ROTARY MOTION THERETO, A FLUID PRESSURE RESPONSIVE MEANS ALSO OPERABLY CONNECTED TO SAID SHAFT FOR IMPARTING AXIAL MOTION THERETO, VALVE MEANS RESPONSIVE TO THE PRESSURE PRODUCED BY THE FLUID PRESSURE PRODUCING MEANS FOR CONTROLLING FLUID FLOW TO AND FROM THE FLUID PRESSURE PRODUCING MEANS AND THE FLUID PRESSURE RESPONSIVE MEANS, AND ADDITIONAL MEANS RESPONSIVE AT THE TERMINAL POSITIONS OF THE WORM WHEREBY THE WORM IS RETURNED TO ITS INITIAL POSITION FOR SUBSEQUENT AXIAL MOVEMENT. 